The problem of providing a simple, low cost, low capacity liquid (water) pressure booster system has been around for a long time. The simplest expedient is a continuously running centrifugal pump piped into the water supply line, and sized for the maximum flow-rate required. During periods of no demand for water, this approach suffers from boiling of the water within the pump volute, causing problems with pump seals, wear rings, and unsuspecting water users. An automatic "thermal purge" valve would solve this immediate problem, but adds water wastage to an already energy wasteful device.
A better method is to develop some way to automatically turn off the booster pump when it is not needed. A switch controlled by the system water pressure is an obvious choice. Whenever the system pressure is deficient, the pump is activated, and vice versa. This works well, except that the resulting continual start/stop cycles soon overheat and destroy the electric motor driving the pump.
This "short-cycling" problem has been eliminated to some extent by combining a hydropneumatic "accumulator" tank with the pressure control switch. The pressure "reservoir" thus provided can serve to lengthen the time the pump remains off by providing pressure for small demands on the system, provided a fairly large accumulator tank is used. In the past, absorption of the tank's air charge into the water was a serious problem, but today built-in flexible isolation bladders can be used to alleviate this problem. However, a serious drawback to the common pump/accumulator system is the bulk and expense involved with an adequately sized accumulator tank.